Advances in horizontal drilling have increased the ability to economically recover hydrocarbons from hydrocarbon bearing formations. However, placement of the horizontal borehole (also known as a lateral) requires particular accuracy. For example, a shale formation may be several thousand feet below the surface, and the shale formation itself may be on the order of 1000 feet thick. Within the illustrative 1000 feet of thickness only a few relatively thin zones, each zone on the order of tens of feet thick, may be suitable locations for placement of the lateral and extraction of hydrocarbons (i.e., target zones). Outside the target zones, some hydrocarbon extraction may be possible, but such extraction is in most cases not economically viable.
Moreover, physical phenomena such as faulting and differential compaction may make the true vertical depth of a target zones different as a function of horizontal location within the hydrocarbon bearing formation. Even if one is able to identify at a particular location a target zone for lateral placement (e.g., at a survey borehole), the precise depth of the target zone may change as a function of distance from the particular location.
Thus, any advance which results in better steering of horizontal boreholes would provide a competitive advantage.